Bump external/bpf_conformance from `4723912` to `90b453f` #1523

Job	Run time
build_windows (Debug, tests)	6m 45s
build_ubuntu (Debug, tests)	8m 6s
build_windows (Debug, library)	4m 10s
build_ubuntu (Debug, library)	1m 2s
build_windows (Release, tests)	6m 40s
build_ubuntu (Release, tests)	5m 46s
build_ubuntu (Release, library)	1m 37s
build_windows (Release, library)	5m 2s
	39m 8s

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